Hardware Fundamentals Week 7 – Lesson 1 23/06/22 Hardware Fundamentals 1
Dec 18, 2015
Hardware Fundamentals
Week 7 – Lesson 1
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Learning Outcomes Define Visual Display Unit (VDU) characteristics: Pixel, Resolution,
Screen size and Refresh Rate Describe briefly the purpose of video standards. Discuss different video standards and high-definition television standards Define Cathode Ray Tube (CRT) characteristics: Dot pitch, Black and
White versus Colour monitors, Two types of pixel shapes, Interlaced, Non-interlaced and Radiation
Describe CRT operation, LCD operation, and Plasma operation Define Liquid Crystal Display (LCD) characteristics: Matrix, Passive
matrix and Active matrix Define Plasma characteristics Compare CRT, LCD and Plasma displays Is CRT still the best for high-definition TV? Surface-conduction Electron-emitter Display (SED) for the future
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Visual Display Unit (VDU) characteristics
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Pixel Picture element The smallest thing that can
be turned on or off to produce an image
A dot Anything you see on a
computer screen is a combination of these dots or pixels
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ResolutionTotal number of pixels displayedResolution = # pixels across * # lines
displayed
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If there are 1024 pixels across and 768 lines displayed, what is the resolution?
Resolution
1024 * 768 = 786,432
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Screen sizeMeasured diagonally
across the front faceMeasured in inchesViewable areas may be
less Typical sizes: (12.1”), 14”, (14.1”),
15”, (15.4”), 17”, 19”, 20”, 21”, 22”, 24”, 27”
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Refresh rateHow often the screen is refreshed or
redrawnScreen needs to be refreshed regularly
as the phosphors stop glowing and the image to be displayed changes
Measured in Hertz (i.e.. Hz) per second
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Video standards
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Video standards Defines the resolution and colorsfor displays The standard used, will be determined by the
monitor and the video adapter card
For high-resolution displays: Quad – is a mode with four times as many pixels
(twice the width and twice the height) Hex – is a mode with 16 times as many pixels (four
times the width and four times the height)
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Video standardsName Resolution Total pixelsColour Graphics Adapter (CGA) 320 x 200 64,000
Enhanced Graphics Adapter (EGA)
640 x 350 224,000
Video Graphics Array (VGA) 640 x 480 307,200
Super VGA (SVGA) 800 x 600 480,000
eXtended Graphics Array (XGA)
1024 x 768 786,432
Super XGA (SXGA) 1280 x 1024 1,310,720
Ultra XGA (UXGA) 1600 x 1200 1,920,000
Quad XGA (QXGA) 2048 x 1536 3,145,728
Quad SXGA (QSXGA) 2560 x 2048 5,242,880
Quad Ultra XGA (QUXGA) 3200 x 2400 7,680,000
Hex Super XGA (HSXGA) 5120 X 4096 20,971,520
Hex Ultra XGA (HUXGA) 6400 X 4800 30,720,00018/04/23 Hardware Fundamentals 11
High Definition Television standards
Name Resolution Total pixels
Wide Quarter VGA (WQVGA)
400 x 240 96,000
Wide VGA (WVGA) 852 x 480 408,960
Wide XGA (WXGA) 1366 x 768 1,049,088
Wide Super XGA (WSXGA) 1600 x 1024 1,638,400
Wide Ultra XGA (WUXGA) 1920 x 1200 2,304,000
Wide Quad XGA (WQXGA) 2560 x 1600 4,096,000
Wide Quad Super XGA (WQSXGA)
3200 X 2048 6,553,600
Wide Quad Ultra XGA (WQUXGA)
3840 X 2400 9,216,000
Wide Hex Super XGA (WHSXGA)
6400 X 4096 26,214,400
Wide Hex Ultra XGA (WHUXGA)
7680 X 4800 36,864,000
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Three types of monitorsCathode Ray Tube (CRT)Liquid Crystal Display (LCD)Plasma
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Three types of monitors
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CRT characteristics and operation
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Dot pitchSpacing between each pixelTypically 0.24mm
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Black and White versus Color monitors
Black and White monitor Use white pixels Made up of one phosphor
Colour monitor Uses three primary colours: Red; Green; and Blue
(RGB) Made up of three phosphors, so close that the
human eye sees the image as one single pixel
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Two types of pixel shapes Triad
Three electron guns arranged with overlapping circles in a triangle
Circular holes in shadow mask Used in smaller screens (e.g. monitors)
Trinitron Three electron guns arranged in one line Three parallel slots Oval slots in shadow mask Used in large screens (e.g. televisions)
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Interlaced Image on screen is created
in two halves First the odd numbered lines
then the even numbered lines
Cheaper Produce a flickering image
and jerky video motion Mostly found on older PC
monitors
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Non-interlaced
Entire screen is created in one goLess flickerSmoother video motionMore commonly found
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CRT operation (1 of 2) Electron gun generates an electron beam The yoke is an electromagnet. Varying the
magnetism in the yoke causes the electron beam to focus in particular areas of the screen
The shadow mask is a metal screen with holes in it. The metal blocks the electron beam but the holes will let the electron beam through when it will strike a pixel, and only one pixel. Makes sure the image is sharp
The phosphor screen is made up of the phosphors that glow when hit by the electron beam. An image is formed by turning on some phosphors but not others.
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CRT operation (2 of 2) The electron beam sweeps over the phosphor
screen, making some phosphors glow, so fast that the user sees a stable image on the screen.
Other components such as the panel glass, funnel glass and the inner magnetic shield provide the structure of the CRT
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Radiation
Whenever an electric current passes through a conductor (such as a wire or a copper track on a circuit board) it gives off an electro magnetic field
The electron gun, electromagnet and coil inside a CRT monitor produce magnetic fields that radiate from the monitor
Most of this radiation is exposed from the rear of the monitor
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LCD characteristics and operation
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MatrixA two dimensional array; that is, an
array of rows and columnsThe background area of colour display
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Two methods are used to apply charges to liquid crystal cells
Passive MatrixActive Matrix
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Passive Matrix Thin Film Transistor (TFT) for each row and
column Cheaper Use relatively few electrodes arranged along
the edges of the liquid crystal layer and rely on timing to be sure the correct cells are charged
The charges in the cells fade quickly, causing a faded look
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Active Matrix Individual TFT’s for each cell/sub pixel (i.e.
RGB) Brighter Wider viewing angle Expensive 70% failure rate at manufacturing stage Provide a more precise and stronger charge,
creating more vivid colours
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LCD operation (1 of 2) Light emanating from a fluorescent panel behind a
computers display panel spreads out in waves that vibrate in all directions
A polarising filter in front of the light panel lets through only the light waves that are vibrating more or less horizontally
In a layer of liquid crystal cells – there is one for each colour (RGB)
The light emerging from each liquid crystal cell passes through one of the three colour filters – RGB – that are arranged close to each other
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LCD operation (2 of 2) The coloured beams of light pass through a second
polarising filter that is aligned to let pass only those light waves that are vibrating more or less vertically
The light that passed through a liquid crystal to which a full electrical charge was applied is now oriented perfectly to pass through the second filter.
Any light that was not twisted at all when passed through the liquid crystals is now blocked completely
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Plasma characteristics and operation
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Plasma characteristics Thin display, less than 2 inches thick Flat display Can be hang on the wall like a painting Plasma display is brighter than LCD Wider viewing angle than LCD (160 degrees) Larger sizes than LCD More expensive than LCD
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Plasma operation (1 of 3) Two sets of electrodes
Address Electrodes are positioned vertically in the rear of the display
Display Electrodes are positioned horizontally in the front of the pixels
These electrodes run through layers of glass and magnesium oxide, which protect and insulate the electrodes from each other
Pixels are called cells, these are depressed in ridges called ribs
The ribs separate the cells Trapped inside each cell is a mixture of xenon and
neon gases
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Plasma operation (2 of 3)
Illuminate tiny coloured fluorescent lights to form an image
Each pixel is made up of three fluorescent lights: a red light; a green light; and a blue light
Display varies the intensities of the different lights to produce a full range of colours
The central element in a fluorescent light is a plasma, a gas make up of free-flowing ions (electrically charge atoms) and electrons (negatively charged particles)
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Plasma operation (3 of 3) When an electrical current runs through a plasma,
negatively charged particles are rushing toward the positively charged areas of the plasma, and the positively charged particles are rushing toward the negatively charged areas
In this mad rush, particles are constantly bumping into each other
These collisions excite the gas atoms in the plasma, causing the plasma screens to release light photons of energy
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CRT versus LCD versus Plasma
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Calculated longer lifeHigher refresh rate
Not affected by magnetic fieldsWider viewing angle
No radiationMore contrast
LighterBrighter colours
Flat more compact screenMore robust
Uses less powerCheaper
LCDCRT
LCD Plasma
Cheaper More expensive
Positioned on desk Hang on the wall
Best image front-on Wider viewing angle
Smaller sizes Larger sizes
Brighter display
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Is CRT still the best for high-definition TV?
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CRT monitor Despite the popularity of LCD and Plasma
screens, the best display of high-definition TV is still the CRT monitor
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SED for the future
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Surface-conduction Electron-emitter Display (SED) Developers are Canon and Toshiba Combines the best of CRT’s, LCD’s and plasma
displays Will have the visual quality of a CRT monitor and the
slimness of LCD and plasma flat panels Requires less materials than LCD and less expensive
circuitry than plasma Screen is made up of phosphors (CRT) painted on the
inside of a plate of glass, each phosphor dot has its own emitter which shoots electrons at only its matching phosphor (no electron beam)
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References Required textbook http://www.howstuffworks.com http://www.webopedia.com http://www.fourmilab.ch/documents/howmanydots/
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